1. Field of the Invention
The invention relates to a recovery system of waste heat from flue gas.
2. Description of the Related Art
In general, the exhaust temperature of the boiler is often controlled to be 140-160° C. To improve the desulfurization efficiency and protect the desulfurizing tower, the exhaust temperature is required to be further decreased to less than 60° C., which means that a lot of heat has to be wasted.
For the benefit of environmental protection, the waste heat is often recycled to heat the feedwater for the boiler. Conventional waste heat recycling devices include low pressure economizers, heat pipe heat exchangers, and phase change heat exchangers.
However, the above three heat exchange technologies all require the wall temperature of the heat exchanger to be more than the acid dew point temperature of the flue gas so as to prevent the devices from corrosion. If the acid dew point temperature of the flue gas is 80° C., to ensure a safety margin, the final exhaust temperature should exceed 100° C.